Honda Insight Tail Extension Project

[3-Wheeler]

Originally Posted by turbothrush

Hi , 3-Wheeler
Congrats on a fantastic project. In a previous post I think you said you used mostly 6 oz cloth. I was wondering how many layers of 6 oz. on the outside. I am planing a project of my own and was thinking 3 layers of 6 oz. on the outside and maybe just 1 or possibly 2 layers on the inside. Any suggestions ?

Hi Turbo,

Yes. The entire outside of the tail has only one layer of 6 ounce glass.

All the exposed edges has a layer of 2 ounce glass, just for protection. These edges are those that come close to the stock bodywork of the car for example.

Where things get a little more complicated are the high stress areas on the INSIDE of the fairing.

Any place where there is some type of mounting going on, there are multiple layers, and in some cases five layers of 6 ounce glass. The fifth layer is about one foot square and covers the embedded wood and metal fasteners inside the wood.

The idea is to fan out the stress out to a wider area in such a way that eventually one layer can support the loads.

This same technique was used to make a full coverage motorcycle fairing that weighed only 13 pounds and is still going strong after almost 20 years of use.

If you make good use of 2 inch thick foam and design the structure correctly, you should easily get by with only one layer of glass over *most* of the surfaces, and then build-up dramatically at any contact points.

Of course careful use of epoxy really helps as well, as the epoxy gives about 30% more strength in bending than wetting out the cloth with Elmer's Wood Glue. Yes, I have prepared samples and measured this. By the way; for those who are very penny conscious Elmer's glue was used on the motorcycle fairing. Just make sure it's sealed against moisture.

Hope this helps, and good luck. Jim.

[euromodder]

Do you have any more news on the fuel efficiency with the full tail, Jim ?

Your fuel log ends where it should become interesting

[3-Wheeler]

Originally Posted by euromodder

Do you have any more news on the fuel efficiency with the full tail, Jim ?

Your fuel log ends where it should become interesting

I've been keeping fuel logs every since the car purchase, so we can keep a running total for any changes made.

The best estimate up to this point was the A-B test run last fall where the car showed an 18% gain at 56 mph.

When the weather warms and the backroads flatten out I plan on doing some A-B-A tests as confirmation of the initial testing, with this next testing being closer to five miles each pass.

Hope this helps, Jim.

[wyatt]

Jim,
I see in post #250, you detail a lot of the materials used. I was wondering where you got your materials. I can get the lumber easily enough, but things like the fiberglass cloth and epoxy resin I am not so sure of. I wouldn't be going for a showroom finish, but I do like the idea of being able to get smooth complex curvature easily from the foam.
Also, you say that Elmer's wood glue can be used in lieu of epoxy, but it has to be sealed. Would sealing with a topcoat (or two) of pigmented epoxy work, or are there better/cheaper ways? Thanks in advance!

Wyatt

[3-Wheeler]

Originally Posted by wyatt

Jim,
I see in post #250, you detail a lot of the materials used. I was wondering where you got your materials. I can get the lumber easily enough, but things like the fiberglass cloth and epoxy resin I am not so sure of. I wouldn't be going for a showroom finish, but I do like the idea of being able to get smooth complex curvature easily from the foam.
Also, you say that Elmer's wood glue can be used in lieu of epoxy, but it has to be sealed. Would sealing with a topcoat (or two) of pigmented epoxy work, or are there better/cheaper ways? Thanks in advance!

Wyatt

Hi Wyatt,

If I recall correctly, U.S. Composites was where I got the cloth and epoxy resin. I used #6 cloth and this is what I have used many times before. For small, tight areas, I selected the thinnest they had at #2 thickness.

If you choose to do multiples layers, like in high stress areas (think mounting), then I would wet out the cloth with resin, and save the Elmers for areas with just one layer. Doing this you can still cover 80% of the tail with Elmers.

Yes, in many ways Elmers Wood Glue is easier than epoxy to work with.

1) A full size motorcycle fairing was made with foam and glass cloth wetted out with Elmers Wood Glue. It is still going strong to this day.

2) In pure bending loads, the Elmers glue has 75% of the strength as epoxy does. This was measured by a two inch thick foam slice that was 2 inches wide and 14 inches long. One sample was wetted out with Elmers glue and the second with West System epoxy. After allowing to sit for several weeks, both samples were tested by loading each beam in the middle and checking for deflection. The Elmers glued piece flexed only 25% more with the same load. From a real world practical standpoint strength wise, they are both equivalent for our purposes.

3) The Elmers glue does need to be sealed in some way to keep rain from contacting it. All the layers of primer and finishing coats on the motorcycle fairing has worked great. The only caution is chipping. If a rock gets kicked up in the road and hits the paint, it can and will cause chipping which needs to be sealed to keep the Elmers glue safe.

4) The Elmers glue wets out the cloth very nicely and adheres well while drying. In this respect it's actually better than resin in my experience. In contrast the West System epoxy is thinner and I have to wait longer to keep the cloth adhering around tight bends before moving on to other areas when bonding the cloth to the foam. If working with a hair dryer, the Elmers glue gets thick very easily and will hold the glass in position very nicely.

5) I would have no reservations about using Elmers on the tail of the car, especially if construction costs were a major concern.

6) A sealing coat of epoxy over the Elmers glue sounds like a good way to seal things up. The epoxy is harder than paint and probably more chip resistant as well. In my experience, the paint can chip off in big chucks (1/2" dia.) if hit by something off the road just right.

Hope this helps, Jim.

[BHarvey]

18%!

Awesome!

[3-Wheeler]

Originally Posted by BHarvey

18%!

Awesome!

* HEADWINDS - TAIL HELPS*

I should mention that several people have approached me to say that the tail mostly helps at speeds 55 mph and higher, and on still-air days this is true.

However, on my way work through-out the year, still-air days are hard to come by. It's usually windy. And on those days when I'm heading into a 15 mph headwind, the tail REALLY helps.

So anyone considering that the benefits of the tail are only realized at highway speeds, well this is only half the story.

Headwinds make the other half on my trips to work, and the tail gives a distinct advantage.

Jim.

[Angmaar]

The boat tail looks great and really "flows" with the rest of the car.

The 18% FE increase is nice too.

[orange4boy]

Great job. The car looks fantastic. Efficiency sure is beautiful!

[3-Wheeler]

Originally Posted by Angmaar

The boat tail looks great and really "flows" with the rest of the car.

The 18% FE increase is nice too.

The "flow" of tail is what really grabbed my attention as well. It's as if Honda had initially designed the car with a longer tail, then at the last minute decided on a shorter shape.

The 18% increase really helps maintain lean burn on those many windy days.

Jim.